This invention relates to a method and apparatus for chemical testing, and more specifically to a method and apparatus for such testing in which samples and/or reagents are manipulated by centrifugal force.
Chemical testing is used in a variety of applications, notably including testing to determine blood chemistries, immunological testing for analyzing fluids and particularly body fluids as well as a host of other liquid analytical chemical techniques, including those done in pollution monitoring activities.
Considering, for example, chemical testing to measure blood chemistries, there are presently in use many chemical techniques to measure, for example, the presence of drugs in the blood stream. In such testing, a sample of blood is isolated from a patient and spun down to separate solid constituents such as red blood cells from the liquid component of the blood. Then the fluid sample remaining is precisely measured, mixed with a measured quantity of reagent and the results of the chemical reaction determined, usually by optical means.
While such testing techniques generally provide accurate results, their performance involves quite a number of tedious and time consuming manual steps, or the use of complex instrumentation in which samples and reagents are contacted with each other and the results measured.
As will be appreciated by those skilled in the art, the techniques described above include the manual isolation of the blood sample, placing it into a centrifuge to effect the solid-liquid separation and then removal of the liquid phase, transferring it from the centrifuge to a sample container which is then placed in an analytical instrument and mixed with the reagents. Some of the more advanced instruments on the market today have the capability of automatically measuring reagents and samples, but nonetheless the manipulative steps involved in the transfer of sample and reagent must still be carried out. The automation of those steps involves the use of complex analytical equipment.
It has been proposed to employ centrifugal force in clinical chemical testing as described in U.S. Pat. Nos. 3,586,484, 3,713,775, 3,744,974, 3,864,089, 3,901,658, 4,237,234 and 4,279,862. The techniques as described in the foregoing patents do not provide any means to change the direction in which the centrifugal force acts, and hence are incapable of utilizing centrifugal force to effect all of the liquid transport functions to completely carry out, from start to finish, the chemical testing operation.
It is accordingly an object of the present invention to provide a method and apparatus which avoids the need to employ tedious manual steps and also avoids the need for complex instrumentation to carry out automated chemical testing.
It is a more specific object of the invention to provide a method and apparatus for carrying out low volume chemical testing which is simple and foolproof in its operation, and involves the use of low-cost instrumentation and equipment.
It is yet another object of the invention to provide a method and apparatus for carrying out chemical testing utilizing centrifugal force to effect liquid transport operations in which the direction of the centrifugal force acting on the fluids can be changed at will.